A cutter assembly wherein material to be cut passes underneath a cutter bar, a track extending under the cutter bar holds a slideable carriage, a rotatable cutter wheel mounts to the carriage, resilient means maintains the side of the cutter wheel against the face of the cutter bar, a releasable gripper bar holds the material against the underside of the cutter bar during the cutting cycle, cords attached to the slideable carriage are used to pull the carriage along the track, and means are provided to attach the assembly to a support. A cutter as above mounted in a frame, and having an electric drive motor with controls for moving the carriage is also disclosed.